In recent years attention has been focused on polythiophenes as functional polymer materials, and studies directed towards the application of such materials as polymeric semiconductors, polymeric conductors, electrochromic materials, electroluminescent materials, and nonlinear optical materials have been reported. These conventional polythiophenes have absorption bands in the visible region of about 450 to 600 nm based on the π-conjugated main chain.
However, in practice, a broader absorption band is desirable, and in this sense the characteristics of conventional polythiophenes have had their limits. For example, to apply polythiophenes as luminescent materials, the absorption band related to the main chain should cover a broad region from ultraviolet to near infrared.
On the other hand, polymers such as poly (diphenylpyridylmethylmethacrylate), synthesized using sparteine-butyllithium as an initiator (e.g. Y. Okamoto et al., J. Am. Chem. Soc., 103, 6971 (1981)), whose main chain construct a one-directional helix are known as polymer materials which recognize enantiomers. These organic polymers having one-directional helices are actually on the market, as column materials for high-performance liquid chromatography, supported on the surface of silica gel, which allows the separation and analysis of optical isomers (Daicel Chemical Industries, Ltd., Chiralpak-OT and Chiralpak-OP).
However, these poly(triphenylmethylmethacrylate)-based materials have a serious disadvantage, in that they lose their enantiomer recognition ability once the side-chain section which fix the main chain helices are released. Hence, if characteristics such as the high resistance to hydrolysis and solvolysis of the helical main chain and the hydrocarbon side chains could be utilized, polythiophenes may be applied as column materials for high-performance liquid chromatography (HPLC) and gas chromatography (GC) which are performed under dark deoxygenated conditions. That is, these materials may be expected to show resistance when used repeatedly for a long period of time.
Also, most column materials presently used for enantiomer recognition, which can be used in separation and analysis by HPLC under reversed phase conditions, are those derived from biological substances most of which are alkyl derivatives containing amide bonds, causing them to deteriorate by hydrolysis. If column materials could be derived from thiophene-based materials containing optically active substituents, or if optically active polythiophenes with helices in the main chain could be supported on carriers, new uses of such materials as column materials for HPLC and GC may be developed.
However, contrary to such anticipations, polythiophenes showing the required performances described above have not been known so far.
The present invention has been carried out under the above circumstances, and its objective is to overcome the limits of conventional technology, to provide novel optically active polythiophenes with strong absorption characteristics due to the main chain in the ultraviolet to visible region, particularly those which exhibit strong main chain absorption characteristics in the ultraviolet-visible region, in solutions at room temperature, and show optical activity by itself, and thiophene monomers which provide such optically active polythiophenes.